Retrospective evaluation of the consequence of alleged patch test sensitization

The risk of actively sensitizing a patient in connection with diagnostic patch tests exists. This risk, however, is extremely low, especially from standard allergens, and if the test is carried out according to internationally accepted guidelines. This retrospective study investigates the clinical consequences in cases of possible patch test sensitization. Among 7619 consecutively tested eczema patients in a 14-year period 26 (0.3%) were identified in the database as having had a late patch test reaction, which may be an indication of patch test sensitization. 9 of these cases were not suitable or available for the follow-up investigation and 3 patients were not traceable. Among the 14 remaining patients 1 had a reaction to gold sodium thiosulphate, which was assessed to be a persistent reaction and not a late reaction, and in 2 patients a clear relevance for the late reacting allergen was found. For the remaining 11 patients we could not rule out that they were patch test sensitized, and they were investigated further. 1 was diseased and 10 were interviewed regarding the possible consequences of the alleged patch test sensitization. 9 had not experienced any dermatitis problems, and 1 could not exclude the possibility that the alleged patch test sensitization had aggravated her dermatitis problems, although we find it unlikely based on the full clinical history. Even though the patient material is small and the limitations inherent in such a retrospective study, the results and the literature indicate that development of clinical contact dermatitis following patch test sensitization is very rare.